<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>倒角</title>
    <style>
        div{
            width: 300px;
            height: 300px;
            background-color: #ff9100;
            border: 1px solid #ff9100;
            border-radius: 180px;
            box-shadow: 0 0 500px 100px #ff9400;
        }
    </style>
</head>
<body>
    <div>

    </div>
</body>
</html>